In a known relay telecommunication network at least three classes of network elements exist: (a) Base station respectively access points, (b) relay nodes and (c) user terminals respectively used equipments. A base station is a fix station which is connected to a wired or wireless backhaul service. A user equipment is a station controlled by a human or autonomous machine, for instance a consumer electronic device or a PDA. A user equipment may communicate with base stations, relay nodes or other user equipments using a wireless link.
A relay station is a fixed or mobile device within a wireless telecommunication network which receives a signal transmitted by a source or another relay node and forwards the received information to a sink or another relay node. A relay node may be part of the infrastructure of a telecommunication network. Using relay nodes in a wireless telecommunication network increases the coverage of an access point to user equipments. Furthermore, deploying relay nodes and access points is a promising solution to build up high capacity mobile telecommunication networks.
A relay telecommunication network is divided into cells. A cell is a set of one base station, a number of relay nodes and user equipments, which are directly connected to the base station or connected via one or several relay nodes to the base station. In a cell of a relay network, several radio connections exist. A radio connection can be decomposed into radio links. For instance, a connection between a base station and a user equipment via a relay node can be decomposed into a first radio link between the base station and the relay node and a second radio link between the relay node and the user equipment.
For providing a high performance data transmission multiple access schemes such as orthogonal frequency division multiple access (OFDMA) are used. In an OFDMA system, chunks are defined by a number of subcarriers in the frequency domain and a number of orthogonal frequency division multiplex (OFDM) symbols in the time domain. Chunks in this respect denote a radio resource allocation in the frequency and in the time domain. By means of a resource allocation process (a) chunks are allocated to links, (b) power is allocated to chunks and (c) a modulation and coding scheme is chosen for a chunk. A resource allocation process must ensure that each connection fulfils its defined quality of service (QoS) constraints such as a minimum data rate and/or a maximum delay for the information propagation.
Known resource allocation processes take into account parameters like channel quality indicator representing the Channel State Information (CSI) about a link, priority information about a link and/or parameters describing the quality of a service transmitted over a link. Such parameters may be for instance a delay, a packet error probability or an average data rate achieved in the past. The parameters taken into account are called resource allocation parameters.
In a relay telecommunication network operating with OFDMA several radio connections are established within a single cell. For each radio connection, a set of Quality of Service (QoS) constraints exists. Since a radio connection can be decomposed into radio links, the QoS constraints of a radio link are defined by the QoS constraints of the corresponding radio connection.
A relay node may have partial or full knowledge of the QoS constraints of the radio links which are served by the relay node. A base station may have full knowledge of the QoS constraints of all the radio links which are served by the base station. If a random access is not preferred for instance due to the capacity loss inherent from collisions, the resource allocation process must be coordinated between the base station, the relay nodes and user equipments within a cell to ensure that the QoS constraints are fulfilled. Therefore the question arises which resource allocation parameters are reported to a unit being responsible for the radio resource allocation in order to properly coordinate the resource allocation process.
A brute force solution for radio resource allocation is that no resource allocation parameters are reported to the base station. The base station and the relay nodes are allocated predefined chunks. In the downlink direction a transmitter which is the base station or one of the relay nodes is allocated a fixed number of chunks. Each transmitter applies its own resource allocation process within its allocated chunks. Thereby, the resource allocation processes of different transmitters are not coordinated. In the uplink direction, a fixed number of chunks are allocated to the base station and to the relay nodes. The chunks are used for reception. This kind of static allocation has the advantage of a low signaling overhead since the resource allocation parameters are not forwarded by a relay node to the base station. The disadvantage is that chunks are used quite inefficiently since the resource allocation process cannot adapt the number of chunks to time varying channel states or time varying traffic load.
In the publication K. -D. Lee, V. C. M. Leung (“Fair Allocation of Subcarrier and Power in an OFDMA Wireless Mesh Network”, IEEE Journal on selected areas in communication, Vol. 24, No. 11, November 2006) a radio resource allocation method is presented for a relay network using OFDMA. Based on CSI averaged over all chunks and given for all radio links and based on knowledge of the traffic of all network elements, a central unit such as for instance a base station or any access point allocates the number of chunks to all network elements of a relay network. Each station performs the power allocation to its chunks. Since a central unit requires the averaged CSI of all radio links and the knowledge of the traffic of all network elements, the signaling overhead is expected to be quite high.
There may be a need for improving the radio resource allocation process for a mobile telecommunication network, wherein on the one hand a proper radio resource distribution between different radio links is realized and on the other hand the data volume used for transmitting signaling information between different network elements is kept within acceptable limits.